Aggregate blocks cover a wide spectrum of solid, cellular (void does not go fully through block) and hollow blocks with densities from 650 to 2400 kg/m3 and range of compressive strengths: Solid blocks from 2.9 to 40N/mm2 and cellular/hollow 2.9 to 22.5M/mm2. Generically they are grouped as ultra lightweight, lightweight and dense (e.g. in thermal bridging details).
Ultra-lightweight aggregate blocks have conductivity not exceeding 0.28 W/mK. Lightweight aggregate blocks have conductivity not exceeding 0.60 W/mK. They are used in both internal and external walls where loading does not require the strength of dense blocks.Their main advantage over dense aggregate blocks comes from a combination of higher insulating properties and a lighter unit weight.
Ultra-lightweight and lightweight blocks are manufactured from cement together with one of a variety of natural or man-made expanded aggregates including: granulated/foamed blast-furnace slag, expanded clay or shale, furnace bottom ash (FBA) and fly ash (FA). The density of the aggregate is generally proportional to the strength of the block.
Dense aggregate blocks with conductivity not exceeding 1.33 W/mK are very much the work-horse of the construction industry. Their distinctive properties of durability and strength make them an ideal and cost-effective solution for all types of load-bearing walls. They have the highest thermal mass of all blocks. Dense aggregate concrete blocks are manufactured from cement, sand and aggregates.
For more information visit the Concrete Block Association at www.cba-blocks.org.uk.